Electronic discharge device of the cavity resonator type



ELECTRONIC DISCHARGE DEVICE OF June 21, 1949. p. L. SPENCER 2,473,827

THE CAVITYBESONATOR TYPE Filed 001;. 5, ,1943

Patented June 21, 1949 UNITED STATES PATENT OFFICE ELECTRONIC DISCHARGE DEVICE OF THE CAVITY RESONATOR TYPE Application October 5, 1943, Serial No. 505,007

13 Claims.

This invention relates to electronic discharge devices, and more particularly to devices of the resonant cavity type for generating, detecting and amplifying ultra high frequency oscillations.

In devices of the type to which the invention relates, the electron emission of the cathode is controlled by the oscillations of the cavity to produce spaced groups of electrons. In such devices the electron transit time should not be greater than one-half of the oscillation period, and preferably less than this. The electron transit time depends upon the distance to be traveled by the electrons and the potential of the anode relative to the cathode. Within the range permitted by the limitation upon the electron transit time to one-half the oscillatory period, I have found it desirable to adjust the distance between the cathode and anode and accordingly alter the capacity therebetween and thereby control within said limits the frequency at which the tube is resonant.

A further object of the invention is to provide an improved tube of the type described in which the space required to be evacuated is greatly reduced.

Further objects of the invention are to provide a tube of the type described which is simple in construction and which may be manufactured on a mass production basis with a minimum of skilled labor and which will nevertheless avoid material variations in the operating characteristics, as between tubes of the same design.

The above and other objects and features of the invention will be made fully apparent to those skilled in the art from a consideration of the following detailed description taken in conjunction with the accompanying drawing in which:

Fig. 1 shows in perspective a tube constructed in accordance with the invention; and

Fig. 2 shows a longitudinal section through the tube of Fig. 1.

Referring to the drawing, the illustrative embodiment of the invention therein shown comprises an annulus I of conductive material, which for convenience of manufacture and assembly may be formed in two or more parts including an upper section 2 and a lower section 3. The sections may be secured together in any suitable manner, such as by the bolts shown or by soldering. The sections define therebetween a portion of a resonant cavity 4. Extending through the central opening in the annulus l is a glass envelope 5 formed of a plurality of sections 6, 'l' and 8. The upper section 6 is separated from the intermediate section I by a diaphragm 9 of conductive material, such as copper, to which the glass sections 6 and 1 are fused or otherwise rigidly connected. The joint between the intermediate section 1 and the diaphragm 9 constitutes an hermetic seal. The joint between the upper section 6 and the diaphragm 9 is not necessarily an hermetic seal, it being sufficient to provide a rigid connection therebetween. The intermediate section 1 is separated from the lower section 8 by a diaphragm l0, also of conductive material, to which the glass of the sections 1 and 8 is fused to form hermetic seals on each side thereof. The upper diaphragm 9 has a central reentrant portion in the form of a boss II projecting downwardly into the intermediate section I and terminating in a fiat surface to form an anode face. The diaphragm III has a central reentrant in the form of a sleeve 12 projecting upwardly into the intermediate section 1 so that the inner end of the sleeve I2 is in close proximity to, but not contacting, the flat face of the boss ll. Within the sleeve [2 is a cathode l3 in the form of a thimble having a flat end face opposing the anode face formed by the boss I I and having lateral surfaces spaced from the internal walls of the sleeve l2 and forming a capacitance therewith. The lower end of the cathode I3 may also have an outwardly projecting flange parallel with the lower surface of the diaphragm It to provide additional capacitive coupling therebetween. A support and cathode lead-in connection I4 is secured to the cathode I3, as by welding, to the flanged end thereof and extends through and is sealed in a press IS in the lower section 8 to provide an electrical connection between the cathode l3 and the external circuit. A heater filament I6 is provided within the oathode l3 and supported by its lead-in wires, which also extend through and are sealed by press it.

The distance between the anode face formed by the boss II and the cathode l3 may be adjusted by means of an adjustable rod I! having a reduced end portion rigidly secured within the boss ll to the diaphragm 9, as by welding. Longitudinal movement may be imparted to the rod I! by means of a screw-threaded portion on the upper end thereof adapted to coact with internal screw threads and an inwardly projecting annular boss l8 formed on a rotatable end cover It. The boss i8 is free to rotate in a central opening in an end cap 20, which end cap closes the upper end of the upper section 6 of the envelope 5. The end cover I9 is provided with a knurled rim projecting downwardly therefrom so that the cover may be angularly adjusted by hand. The threads on the rod l1, and the coacting threads in the boss it, may be relatively fine so that a comparatively large angular movement of the end cover I 9 results in only a small longitudinal movement of the rod IT. The diaphragm 9 may be provided with an annular corrugation surrounding the boss ii to facilitate deformations thereof during the adjustment of the rod l1. When the rod has been adjusted to the desired position, it may be locked in such position by means of a knurled locking nut 2|.

An annular clamping nut 22 is provided with external screw threads adapted to coact with internal screw threads in the central opening of the upper section 2 of the annulus I to clamp the diaphragm 9 securely against an internal shoulder in the upper section 2. A similar clamping nut 23 is provided for clamping the diaphragm ID in the lower section 3 of the annulus l.

A coupling loop 24-is provided in the resonant chamber 4 having: one end thereof secured to-the interior wall of the-chamber, and the other end connected to a wire 25 extending through an opening 26. The'wire2-5 may be-eitheran input transit line for ultra highi'frequency oscillations in case that the tubeis-used as a detector, or it may be an output line when the tube is used as a generator. A concentricline,constructed in the manner known in the art,,may be provided, or an open line may. be used; Only'that portion of the tube enclosed in the'lower. section Band the intermediate; section 1 of the. envelope need be evacuated. Since. by this construction a the resonant cavity disnotevacuated, the opening 26 need not be'sealed.

In the operationxof devices'of this type, it will be understood that when the: device is used as a detector or amplifier, modulated radio frequency energy is received from. the line and the coupling loop 24, and'is' transferred to the resonant cavity 4-to-cause the-standing waves therein to be correspondingly modulated.

It will be understoodthat the" diaphragms 9 and H), being electrically connected to the annulus I, together with the reentrant portions II and I2 thereof constitute-a part of the oscillatory circuit of the resonant cavity 4. The cathode l3, being capacitively coupled to the diaphragm ID, isalso a part of the cavity circuit, and thelines. of electric. force of the standing waves are at their. greatest-intensity in the space between theopposing faces of the cathode and anode and in a direction: parallel to the path of the electrons therebetween. Variations in the standing waves, due to modulationof the received signal, therefore: producevariations in the anode-cathode current, which in turn produce modulation frequency output currents in the external anode-cathode circuit.

As is well-known, the, electron transit time in such a device must be-less? than a half period of the oscillations of the standing. waves, and preferably is less than"this; It is therefore necessary that the distance between the cathode and the opposed anode facebe so correlated to the anode'voltage. that therelectron: transit time does not exceedthe' permitted value.- It will be evident thatv the distance between the cathode and the. opposing anode face also affects the capacitance therebetweemandsince thecathode is capacitively couple'dzinz the oscillation cavity the distance between the: cathode and anode also affects the characteristics of the resonant 4 cavity. I haVe found that, by adjusting the distance between the anode face and the cathode, Within the limits permitted by th limitation upon the electron transit time, the frequency at which the cavity is resonant may be adjusted.

The construction provides a means for making fine adjustments of the anode face relative to the cathode, and accordingly permits close adjustments of the resonance frequency of the device.

It will be observed that by providing a construction in which that portion of the wall of the resonant cavity electrode which forms the anode face also forms one of the walls enclosing the evacuated space of the tube, the adjustments described in the foregoing may be effected entirely from the exterior of such evacuated space. Tuning rods or other mechanisms within the evacuated space are obviated, as well as the complicated mechanisms and expedients required to effect the movement of such rods within the sealed space from the exterior of the tube.

As is Well-known in this art, it is frequently required that two or more tubes, comprising a system or involved in a transmitter and one or more receivers, have substantially identical characteristics. Since slight variations in the manufacture of such devices result in material variations in resonance frequency of the tubes, the manufacture of such devices in quantity ordinarily requires high skill and precision. This greatly retards quantity production and increases the cost of the. product.

Devices of the present invention do not require such high. precision in the manufacture thereof, particularly with respect to the anodecathode spacing, but may be constructed of parts requiring relatively little machining. and none of this to close tolerances. It is sufficient that the-dimensions of the members forming the annulus l and the diaphragms 9 and i0 provide an easy approximation to the desired resonance frequency of the cavity defined thereby and, after assembling, the device may be adjusted to the precise resonance frequency desired and locked in the adjusted position.

While the invention has been described by means of a specific embodiment, other embodiments within the scope of the appended claims will be obvious to those skilled in the art from a consideration of the embodiment shown. It will be understood that the parts comprising the annulus I may be formed by casting, or since this member need not have the relative thickness shown, the parts thereof may be formed of stampings or in similar manner. The diaphragms 9 and i0 may be attached to the annulus l by other means than the clamping nuts shown. It is sufficient that they be electrically connected to the annulus, which connection may be effected by brazing, Welding or otherwise.

It Will be apparent that certain features of the invention possess utility entirely apart from the important feature of tuning, and that the tuning means possesses utility in connection with some tubes other than the simple diode shown.

What is claimed is:

1. An electronic discharge device comprising a glass envelope, a diaphragm extending transversely through said envelope and having a circumferential portion projecting externally thereof, said envelope being hermeticallysealed to said diaphragm on both sides thereof, said envelope having an hermetically'sealed' space on one side of said diaphragm, a second diaphragm extending across said envelope on the opposite side of said first-mentioned diaphragm from said space and hermetically sealed to said envelope on the side thereof facing said first-mentioned diaphragm.

2. An electronic discharge device comprising a glass envelope, a diaphragm extending transversely through said envelope and having a circumferential portion projecting externally thereof, said envelope being hermetically sealed to said diaphragm on both sides thereof, said envelope having an hermetically sealed space on one side of said diaphragm, a second diaphragm extending across said envelope on the opposite side of said first-mentioned diaphragm from said space and hermetically sealed to said envelope on the side thereof facing said first-mentioned diaphragm, and means exterior of said space connecting said first-mentioned diaphragm peripherally to said second diaphragm.

3. An electronic discharge device comprising a glass envelope, a diaphragm extending transversely through said envelope and having a circumferential portion projecting externally thereof, said envelope being hermetically sealed to said diaphragm on both sides thereof, said envelope having an hermetically sealed space on one side of said diaphragm, a second diaphragm extending across said envelope on the opposite side of said first-mentioned diaphragm from said space and hermetically sealed to said envelope on the side thereof facing said first-mentioned diaphragm, a cathode positioned in an opening in said first-mentioned diaphragm, and an anode face on said second diaphragm projecting toward said cathode.

4. An electronic discharge device comprising a glass envelope, a diaphragm extending transversely through said envelope and having a circumferential portion projecting externally thereof, said envelope being hermetically sealed to said diaphragm on both sides thereof, said envelope having an hermetically sealed space on one side of said diaphragm, a second diaphragm extending across said envelope on the opposite side of said first-mentioned diaphragm from said space and hermetically sealed to said envelope on the side thereof facing said first-mentioned diaphragm, a cathode positioned in an opening in said first-mentioned diaphragm and capacitively coupled thereto, an anode face on said second diaphragm projecting toward said cathode, and means exterior of said space connecting said first-mentioned diaphragm peripherally to said second diaphragm.

5. An electronic discharge device comprising a glass envelope, a pair of diaphragms extending transversely through said envelope, one of said diaphragms being imperforate and providing an anode face projecting toward the other of said diaphragms, said other diaphragm having an open ended sleeve projecting toward said anode face, a cathode within said sleeve having a face opposing and in close proximity to said anode face, and means electrically connecting said diaphragms exteriorly of said envelope and defining therewith a cavity resonator.

6. An electronic discharge device comprising a glass envelope, a pair of diaphragms extending through said envelope, one of said diaphragms being imperforate and providing an anode face projecting toward the other of said diaphragms, said other diaphragm having an open ended sleeve projecting toward said anode face, a cathode within said sleeve having a face opposing and in close proximity to said anode face, means electrically connecting said diaphragms exteriorly of said envelope and defining therewith a cavity resonator, and means coupled to said imperforate diaphragm for moving said anode face toward and away from said cathode.

'7. An electronic discharge device comprising a glass envelope enclosing an evacuated space, a pair of diaphragms extending transversely through said envelope, one of said diaphragms being imperforate and providing an anode face projecting toward the other of said diaphragms, said other diaphragm having an open ended sleeve projecting toward said anode face, a cathode within said sleeve having a face opposing and in close proximity to said anode face, and means electrically connecting said diaphragms exteriorly of said envelope and defining therewith a cavity resonator, said imperforate diaphragm forming one of the walls of the evacuated space of said envelope.

8. An electronic discharge device comprising a glass envelope encircling an evacuated space, a pair of diaphragms extending transversely through said envelope, one of said diaphragms being imperforate and providing an anode face projecting toward the other of said diaphragms, said other diaphragm having an open ended sleeve projecting toward said anode face, a cathode within said sleeve having a face opposing and in close proximity to said anode face, means electrically connecting said diaphragms exteriorly of said envelope and defining therewith a cavity resonator, said imperforate diaphragm forming one of the walls of the evacuated space of said envelope, and means coupled to said imperforated diaphragm exteriorly of said evacuated space for flexing said imperforate diaphragm to move said anode face toward and away from said cathode.

9. An electronic discharge device comprising a glass envelope providing an evacuated space, a pair of spaced electrode elements in said envelope, a cavity resonator surrounding said envelope and providing an enclosed space exterior of said evacuated space of said envelope, said electrodes being electrically connected through said cavity resonator, and means coupled to one of said electrode elements for altering the distance between said spaced electrode elements.

10. An electronic discharge device comprising a glass envelope providing an evacuated space, a pair of spaced electrode elements in said envelope, a cavity resonator surrounding said envelope and providing an enclosed space exterior of said evacuated space of said envelope, said electrodes being electrically connected through said cavity resonator, and means coupled to one of said electrode elements externally of said evacuated space for altering the distance between said spaced electrode elements.

11. An electron discharge device including an evacuated container enclosing means for developing an electron stream, means defining a cavity resonator for modulating said electron stream, said cavity resonator having a wall exterior of said evacuated chamber and a second wall constituting a wall of said evacuated chamber, and means coupled to said wall of said evacuated chamber on the exterior of said evacuated chamber for flexing said wall of said evacuated chamber to tune the cavity resonator.

12. In combination with an elongated hollow conductive structure adapted to function as a guide for electricity of ultra-high frequency, an

electron discharge device coupled to said guide structure and comprising a hollow body resonator, opposed anode and cathode elements enclosed thereby, and means for flexing a wall of said resonator to simultaneously tune the same and adjust the gap between said electrode anode and cathode elements.

13. An electron discharge device comprising a hollow body resonator, opposed anode and cathode elements enclosed thereby, means for flexing a wall of said resonator to simultaneously tune the same and adjust the gap between said anode and cathode elements, and means adjacent one of said elements for initiating the passage of current therebetween.

PERCY L. SPENCER.

8 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,167,201 Dallenbach July 25, 1939 2,263,184 Mouromtseff et a1. Nov. 18, 1941 2,283,895 Mouromtsefi et a1. May 19, 1942 2,298,949 Litton Oct. 13, 1942 2,309,966 Litton Feb. 2, 1943 2,353,742 McArthur July 18, 1944 2,394,397 Mouromtsefi et a1. Feb. 5, 1946 2,400,753 Haefi May 21, 1946 2,407,974 Clifiord et al. Sept. 24, 1946 2,413,171 Clifford et a1. Dec. 24, 1946 2,415,962 Okress Feb. 18, 1947 

